<?php

if (! defined ( 'BASEPATH' ))
	exit ( 'No direct script access allowed' );
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package		CodeIgniter
 * @author		ExpressionEngine Dev Team
 * @copyright	Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license		http://codeigniter.com/user_guide/license.html
 * @link		http://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */

// ------------------------------------------------------------------------


/**
 * Database Cache Class
 *
 * @category	Database
 * @author		ExpressionEngine Dev Team
 * @link		http://codeigniter.com/user_guide/database/
 */
class CI_DB_Cache {
	
	var $CI;
	var $db; // allows passing of db object so that multiple database connections and returned db objects can be supported
	

	/**
	 * Constructor
	 *
	 * Grabs the CI super object instance so we can access it.
	 *
	 */
	function CI_DB_Cache(&$db) {
		// Assign the main CI object to $this->CI
		// and load the file helper since we use it a lot
		$this->CI = & get_instance ();
		$this->db = & $db;
		$this->CI->load->helper ( 'file' );
	}
	
	// --------------------------------------------------------------------
	

	/**
	 * Set Cache Directory Path
	 *
	 * @access	public
	 * @param	string	the path to the cache directory
	 * @return	bool
	 */
	function check_path($path = '') {
		if ($path == '') {
			if ($this->db->cachedir == '') {
				return $this->db->cache_off ();
			}
			
			$path = $this->db->cachedir;
		}
		
		// Add a trailing slash to the path if needed
		$path = preg_replace ( "/(.+?)\/*$/", "\\1/", $path );
		
		if (! is_dir ( $path ) or ! is_really_writable ( $path )) {
			// If the path is wrong we'll turn off caching
			return $this->db->cache_off ();
		}
		
		$this->db->cachedir = $path;
		return TRUE;
	}
	
	// --------------------------------------------------------------------
	

	/**
	 * Retrieve a cached query
	 *
	 * The URI being requested will become the name of the cache sub-folder.
	 * An MD5 hash of the SQL statement will become the cache file name
	 *
	 * @access	public
	 * @return	string
	 */
	function read($sql) {
		if (! $this->check_path ()) {
			return $this->db->cache_off ();
		}
		
		$segment_one = ($this->CI->uri->segment ( 1 ) == FALSE) ? 'default' : $this->CI->uri->segment ( 1 );
		
		$segment_two = ($this->CI->uri->segment ( 2 ) == FALSE) ? 'index' : $this->CI->uri->segment ( 2 );
		
		$filepath = $this->db->cachedir . $segment_one . '+' . $segment_two . '/' . md5 ( $sql );
		
		if (FALSE === ($cachedata = read_file ( $filepath ))) {
			return FALSE;
		}
		
		return unserialize ( $cachedata );
	}
	
	// --------------------------------------------------------------------
	

	/**
	 * Write a query to a cache file
	 *
	 * @access	public
	 * @return	bool
	 */
	function write($sql, $object) {
		if (! $this->check_path ()) {
			return $this->db->cache_off ();
		}
		
		$segment_one = ($this->CI->uri->segment ( 1 ) == FALSE) ? 'default' : $this->CI->uri->segment ( 1 );
		
		$segment_two = ($this->CI->uri->segment ( 2 ) == FALSE) ? 'index' : $this->CI->uri->segment ( 2 );
		
		$dir_path = $this->db->cachedir . $segment_one . '+' . $segment_two . '/';
		
		$filename = md5 ( $sql );
		
		if (! @is_dir ( $dir_path )) {
			if (! @mkdir ( $dir_path, DIR_WRITE_MODE )) {
				return FALSE;
			}
			
			@chmod ( $dir_path, DIR_WRITE_MODE );
		}
		
		if (write_file ( $dir_path . $filename, serialize ( $object ) ) === FALSE) {
			return FALSE;
		}
		
		@chmod ( $dir_path . $filename, FILE_WRITE_MODE );
		return TRUE;
	}
	
	// --------------------------------------------------------------------
	

	/**
	 * Delete cache files within a particular directory
	 *
	 * @access	public
	 * @return	bool
	 */
	function delete($segment_one = '', $segment_two = '') {
		if ($segment_one == '') {
			$segment_one = ($this->CI->uri->segment ( 1 ) == FALSE) ? 'default' : $this->CI->uri->segment ( 1 );
		}
		
		if ($segment_two == '') {
			$segment_two = ($this->CI->uri->segment ( 2 ) == FALSE) ? 'index' : $this->CI->uri->segment ( 2 );
		}
		
		$dir_path = $this->db->cachedir . $segment_one . '+' . $segment_two . '/';
		
		delete_files ( $dir_path, TRUE );
	}
	
	// --------------------------------------------------------------------
	

	/**
	 * Delete all existing cache files
	 *
	 * @access	public
	 * @return	bool
	 */
	function delete_all() {
		delete_files ( $this->db->cachedir, TRUE );
	}

}


/* End of file DB_cache.php */
/* Location: ./system/database/DB_cache.php */